Subjects

Relapse remains the major cause of mortality after hematopoietic cell transplantation (HCT) for pediatric acute leukemia. Previous research has suggested that reducing the intensity of calcineurin inhibitor-based graft-versus-host disease (GVHD) prophylaxis may be an effective strategy for abrogating the risk of relapse in pediatric patients undergoing matched sibling donor (MSD) HCT. We reasoned that the benefits of this strategy could be maximized by selectively applying it to those patients least likely to develop GVHD. We conducted a study of risk factors for GVHD, to risk-stratify patients based on age. Patients age <18 years with leukemia who received myeloablative, T cell-replete MSD bone marrow transplantation and calcineurin inhibitor-based GVHD prophylaxis between 2000 and 2013 and were entered into the Center for International Blood and Marrow Transplant Research registry were included. The cumulative incidence of grade II-IV acute GVHD (aGVHD) was 19%, that of grade II-IV aGVHD 7%, and that of chronic GVHD (cGVHD) was 16%. Compared with age 13 to 18 years, age 2 to 12 years was associated with a lower risk of grade II-IV aGVHD (hazard ratio [HR],.42; 95% confidence interval [CI],.26 to.70; P =.0008), grade II-IV aGVHD (HR,.24; 95% CI,.10 to.56; P =.001), and cGVHD (HR,.32; 95% CI,.19 to.54; P <.001). Compared with 2000-2004, the risk of grade II-IV aGVHD was lower in children undergoing transplantation in 2005-2008 (HR,.36; 95% CI,.20 to.65; P =.0007) and in 2009-2013 (HR,.24; 95% CI..11 to.53; P =.0004). Similarly, the risk of grade III-IV aGVHD was lower in children undergoing transplantation in 2005-2008 (HR,.23; 95% CI,.08 to.65; P =.0056) and 2009-2013 (HR,.16; 95% CI,.04 to.67; P =.0126) compared with those doing so in 2000-2004. We conclude that aGVHD rates have decreased significantly over time, and that children age 2 to 12 years are at very low risk for aGVHD and cGVHD. These results should be validated in an independent analysis, because these patients with high-risk malignancies may be good candidates for trials of reduced GVHD prophylaxis.